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US upgrades GPS augmentation

The FAA is updating its Wide Area Augmentation System (WAAS) to improve its accuracy, integrity and availability.

It has awarded a contract to NovAtel to produce and deliver 40 new Ground Uplink Station (GUS) signal generators. The company will also provide engineering support services for its other SBAS products currently in use, including third-generation reference receivers.

In 2003, WAAS was the first of a series of satellite-based augmentation systems (SBAS), which improve the accuracy, availability and integrity of GPS-derived position information. Using WAAS, GPS signal accuracy is improved to ~1.5 m in both the horizontal and vertical.

WAAS has been replicated in other global areas, including: the European Geostationary Navigation Overlay Service (EGNOS), Japan’s Multi-functional Satellite Augmentation System (MSAS) and the Indian GPS Aided Geo Augmented Navigation (GAGAN).

As SBAS corrections are transmitted from geostationary satellites on the GPS L1 and L5 frequencies, no additional receiver is required to access the augmentation - but receiver software must be modified to use it.

Although SBAS has been introduced by aviation authorities primarily to enable precision runway approaches without requiring a ground infrastructure, the enhanced GPS service is nowadays used by millions of receivers in land and sea environments as well.